The liver is the main organ concerned with the metabolism of foreign chemicals, including carcinogens. Liver cancer can be induced by a variety of compounds after prolonged administration to experimental animals. Under some circumstances, however, including the administration of large single carcinogenic doses sufficient to produce tumors in other organs, liver cancer does not appear, even though the extent of interaction between the carcinogen with macromolecules is greater in the liver than in the other organs. There is evidence that the liver has a greater capacity for repair of carcinogenic damage to its genetic material than other organs and also that it may tend to exert a protective action against ingested carcinogens by retaining a greater part of the carcinogenically active metabolites, particularly at lower dose levels. Experiments are planned to investigate this apparent protective function of the liver using various nitrosamines and other chemical carcinogens. BIBLIOGRAPHIC REFERENCES: Kim, S., Lotlikar, P.D., Chin, W. and Magee, P.N. Protein Bound Carboxyl-Methyl Ester as a Precursor of Methanol Formation During Oxidation of Dimethylnitrosamine In Vitro. Cancer Letters 2:279-284 (1977). Magee, P.N. Covalent Binding and Endogenous Incorporation as Illustrated by Nitroso Carcinogens. J. Tox. Environ. Health 2:883-893 (1977).